Project 3 extends the ITC survey methodology outlined in Project 1, by undertaking supplementary data collection in six ITC countries, two developed (i.e., US &UK) and four LMICs (i.e., China, Malaysia, Mexico, Thailand) with the goal of examining variation in cigarette characteristics among leading brand varieties, and exploring how these differences relate to tobacco control policies, tobacco uses behaviors, and exposure to selected tobacco smoke constituents in different countries. Project 3 has three specific aims. Aim 1 involves tracking the tobacco market and establishing a repository of leading cigarette brands, linkable to retailer-level evaluations of product marketing and pricing activities. Aim 2 has two components related to the construction and composition of cigarettes: (a) characterizing cigarettes obtained for the repository as well as from individuals for key design and physical features that can influence smoke chemistries and consumer acceptability;and (b) developing a panel of physical features of cigarettes brands that can be used to reliably distinguish legitimate from counterfeit brands. Aim 3, which seeks to examine person-level variation in smoking behaviors and exposures, also involves two components: (a) examining in a subsample of the ITC cohort participants in Project 1 the extent to which variation in tobacco use behaviors can be explained by measures of nicotine intake and nicotine metabolism;and (b) comparing how tobacco use behaviors, nicotine intake and nicotine metabolism are related to indicators of social deprivation/socioeconomic status, both within and between high resource and LMICs. RELEVANCE (See instructions): The proposed project seeks to understand how and why differences in smokers and products may or may not influence reactions to tobacco control policies in different countries. Understanding these issues can provide important information to increase the effectivenessof these policies to help smokers quit and avoid tobacco use.